Weighted nonaqueous drilling fluid



V As is well known in the art customary to circulate from the surface to the -to make a mud of very high Patented Apr. 22, 194i 7 George E. Cannon and Company, a corporation of Delaware No Drawing. Application April13,1938,

SerialNo. 201,724 10 Claims. (Cl. 255-1)" The present invention is directed to a non-. than ten carbon atoms in the molecule can be aqueous drilling'mud of high weight;

In the drilling zof oil Gulf-Coast, considerable trouble is encountered when itbecomesnecessa y to drill through a certain type of shale .known as heaving shale which is evidently bentonitic in character. Many opinions havebe'en expressed as to the reasons for this difficulty but it is generally acknowledged that the main reasonis the effect of water on the shale, causing it to swell. Accordingly, it has been suggested to use -noii'afqueous drilling mud, for example, oil.

The object of the I vision of a nonaq'ueous. drilling mud, specifically an oil base drilling mud, of greater weight and stability than has hitherto been possible of V achievement. Briefly, the present invention redrilling operations of an oil sides in the use=in carrying an oxide of lead such as litharge. More specifically, theflpresent invention contemplates the addition to an quantities of litliarge of an agent capable of holding the litharge in suspension.

bottom of the borehole and back to the surface a drilling fluid thefunction of which is to lubricate. and cool the drillingbit and to carry the cuttings to the surface. Ordinarily such fluids are composed of water and a suitable clay, and may or may notinclude a weighting material such as inorganic compounds of high speciflc'gravity. In the practice of the present invention the same procedure is followed except that an oil base mud carrying a compound or lead is substituted for the conventional aqueous mud and, in general, the oil base muds employed according to the present invention are of greater weight than the conventional drilling fluids.

As previously indicated, the present invention contemplates broadly the use of lead compounds, such as litharge, in oil base drilling fluids. These compounds have the peculiar advantage that they are readily wettable by oil. When it is desired weight, however, it is found that these lead compounds tend to settle rapidly from the oil base, thereby rendering the drilling fluid unsuitable for use as a circulating medium for carrying out cuttings from the borehole. It has been found that this tendency to settle out is eliminated by the use of suitable quantities of fatty acids of high molecular weight and, particularly, unsaturated fatty acids, such as oleic acid. -In general, fatty acids having more wells, especially in the present invention is the prooil base mud containing large I of drilling wells, it

waren'mn NoNAQUEOUS panama FL Milton Williams, Houston, Tex., assignors to Standard Oil Development employed. By this-expedient it is possible to produce a mud having a density of the order of the shale to be drilled through which is one of the ob- 5 jectives of the present invention.

When the fatty acid is added to'the suspension:

of lead compound in oil it produces a mixture which has the appearance of clabber, that is, the lead compound tends to agglomerate although it remains in suspension. This agglomeration can be prevented by adding to the mixture an ester of a fatty acid, such as a vegetable or animal oil.

atory. 4

Crude oil: AMhmi-t A. P. l. lithcm'e:

Olelc Weight lbsJgel' fil'gf'fi; @500 c 23 3 831 Settling umc 16.6 S ettledtoo rapidly 0 Immediately. l6.6.... --.-do 0.5 Do.

16 a do 1. 0 Do. in a 300 1. 5 Stable.

Settled too rapidly 0.76 Immediately -do.. 0. 75 Do. 0.75 D0.

1.0 Stable. 1.25 Do. 1. 5 Do. '1. 75 D0. 2.0 Do. 2.25 Do. 2.5 Do. 1.25 Do.

Less than 1% in 24 hours As can be seen from the above table the amount of oleic acid which is. necessary to render the suspension stable, decreases with the amount of lead in suspension. For example, with sufflcient lead to make a mud weighing 16.6 pounds per gallon, it was necessary to add 1.5 parts of oleic acid by volume in order to produce stability. With sumcient litharge to make a 26 pound mud on the other hand, 1% by volume of the oleic acid was suilicient for stability.

In general, the fatty acid is employed in amounts varying from about 1% to 4% by volume of the drilling fluid. Of course, greater amounts In the-following table is shown the efiect o1 headings over. the various columns render the table self explan can be used. When a vegetable .or animal 01! is.

increasing the stability of suspensions or, lead oxide in oil by the addition thereto of fatty. acids. It is intended to claim this invention as broadly as the prior art permits .in the appended claims.

We claim:

1. A stable drilling fluid comprising a suspension of an oxide of lead in a petroleum oil to which has been added at least one percent by volume of a fatty acid.

2. A-drilling fluid comprising a'sus'pension' oi. litharg'e in a petroleum oil t0- which has been adidled at least one percent by volume of a fatty ac a 3. A drilling fluid comprising a suspension of an oxide or lead in a petroleum oil to which has been added at least. one an unsaturated fatty. acid.

4:, A drilling fluid comprising a suspension of lithar'ge in a petroleum oil to which has been added at least one percent by volume of an unsaturated iatty acid.

percent by volume pt sion of litharge in a petroleum on to which has '15 an oleic acid.

5. A stable drilling fluid comprising a suspension of an oxide of lead in a petroleum oil to which has been added at least one percent by volume of oleic acid; v

'6. A stable drillin fluid comprising a suspension of litharge in petroleum. oil to which has been added at least one percent by volume 01 'l. A stable drilling fluid comprising a' suspens1on ot an oxide of lead in a petroleum oil to which has been added a small amount or a mixture of a fatty acid and-a glyceride 01 a fatty acid.

8. A stable drilling fluid comprising a suspenbeen added a small amount of amixture of a fatty acid and a glyceride or a fatty acid. g 9. A stabledrilling fluid comprising a suspension 01' an oxide of lead in a petroleum oil to which has been added a small amount oi amixture of oleic acid and a vegetable oil. 1 10. A drilling fluid comprising a suspension GEORGE E. CANNON. MILTON WILLIAMS.

of litharge in a petroleum oil to which'has'been added a small amount of a mixtin'e. of oleic acid a and a vegetable. oil; 

